Operating machines for industrial use such as construction machinery will have a significant influence if they stop due to failure or other causes. Thus these machines are often subject to preventive maintenance that keeps the machines in an optimized state. What is generally carried out is periodic maintenance mainly by reference to the operating time. Components of the machines are inspected, overhauled, and replaced as per design criteria and in accordance with the operating time of the machines.
As long as preventive maintenance is performed, the machines should not fail because their good conditions are kept up. In practice, however, they inevitably fail and stop. For example, if a machine is used under loads greater than what is expected by design criteria, its components can run down faster than expected and cause the machine to fail and stop. That is, the cause of component failure lies in a mismatch between stipulated design criteria and the operating conditions in the actual operating environment.
In view of the above, there have been disclosed an invention whereby the time for maintenance and replacement of each of the components of a machine is totaled and statistically processed to obtain the actual life spans of the components for practical use (PCT Patent Publication No. WO01/073215 Pamphlet) and an invention whereby the life spans of components are estimated in accordance with operating time and location (JP-2005-173979-A). Also disclosed is an invention whereby the usage limit of a machine is estimated based on sensor reference values and the rates of change in sensor values with regard to the model of the machine and the failure mode of its components (JP-2002-352024-A).